Umbilical for Use in Subsea Applications

ABSTRACT

An umbilical ( 600 ) for the transfer of fluids and/or electric current/signals, particularly between the sea surface and equipment deployed on the sea bed (e.g., in deep waters), is provided. The umbilical contains a plurality of elongated umbilical elements (e.g., two or more), such as a channel element ( 603 ), fluid pipe ( 604 ), electric conductor/wire ( 606 ) (e.g., optic fiber cable), armoring wire, etc., enclosed within an outer sheath (e.g., plastic sheath). The umbilical also contains at least one reinforcing rod ( 607 ) formed from a plurality of unidirectionally aligned fiber rovings embedded within a thermoplastic polymer matrix. The present inventors have discovered that the degree to which the ravings are impregnated with the thermoplastic polymer matrix can be significantly improved through selective control over the impregnation process, and also through control over the degree of compression imparted to the ravings during formation and shaping of the rod, as well as the calibration of the final rod geometry. Such a well impregnated rod has a very small void fraction, which leads to excellent strength properties for reinforcing the umbilical elements.

This application relates to U.S. Provisional Patent Application Ser. No.61/474,467, filed Apr. 12, 2011, titled: “UMBILICAL FOR USE IN SUBSEAAPPLICATIONS”, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Umbilicals are often used in the transmission of fluids and/or electricsignals between the sea surface and equipment located on the sea bed.Such umbilicals generally include one or more pipes and electricconductors/wires collected in a bundle, a filler material arranged atleast partly around and between the pipes and conductors/wires, and aprotective sheath enclosing the pipes, conductors/wires, and fillermaterial. To help strengthen such umbilicals, attempts have been made touse pultruded carbon fiber rods as separate load carrying elements.Exemplary umbilical designs are described in more detail, for instance,in U.S. Pat. No. 7,798,234 to Ju, et al. and U.S. Pat. No. 7,754,966 toFigenschou, which are incorporated herein in their entirety by referencethereto for all purposes. A significant problem with such rods however,it is that they rely upon thermoset resins (e.g., vinyl esters) to helpachieve the desired strength properties. Thermoset resins are difficultto use during manufacturing and do not possess good bondingcharacteristics for forming layers with other materials.

As such, a need currently exists for an umbilical that containspultruded fiber rods formed from a thermoplastic material, which arestill capable of achieving the desired strength and durability.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, an umbilicalfor use in subsea applications is disclosed. The umbilical comprises aplurality of umbilical elements extending in a longitudinal direction,at least one reinforcing rod, and an outer sheath enclosing theumbilical elements and the reinforcing rod. The rod has a core thatcontains a plurality of thermoplastic impregnated rovings comprisingcontinuous fibers oriented in the longitudinal direction and athermoplastic matrix that embeds the fibers. The continuous fibersconstitute from about 25 wt. % to about 80 wt. % of the core and thethermoplastic matrix constitutes from about 20 wt. % to about 75 wt. %of the core.

Other features and aspects of the present invention are set forth ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures, in which:

FIG. 1 is a system that may be used in conjunction with one embodimentof the umbilical of the present invention;

FIG. 2 is a cross-sectional view of one embodiment of the umbilical ofthe present invention;

FIG. 3 is a cross-sectional view of another embodiment of the umbilicalof the present invention;

FIG. 4 is a cross-sectional view of yet another embodiment of theumbilical of the present invention;

FIG. 5 is a perspective view of one embodiment of a consolidated ribbonfor use in the present invention;

FIG. 6 is a cross-sectional view of another embodiment of a consolidatedribbon for use in the present invention;

FIG. 7 is a schematic illustration of one embodiment of an impregnationsystem for use in the present invention;

FIG. 8 is a cross-sectional view of the impregnation die shown in FIG.7;

FIG. 9 is an exploded view of one embodiment of a manifold assembly andgate passage for an impregnation die that may be employed in the presentinvention;

FIG. 10 is a perspective view of one embodiment of a plate at leastpartially defining an impregnation zone that may be employed in thepresent invention;

FIG. 11 is a schematic illustration of one embodiment of a pultrusionsystem that may be employed in the present invention;

FIG. 12 is a perspective view of one embodiment of a continuous fiberreinforced thermoplastic rod that may be formed in accordance with thepresent invention;

FIG. 13 is a top cross-sectional view of one embodiment of variouscalibration dies that may be employed in accordance with the presentinvention;

FIG. 14 is a side cross-sectional view of one embodiment of acalibration die that may be employed in accordance with the presentinvention;

FIG. 15 is a front view of a portion of one embodiment of a calibrationdie that may be employed in accordance with the present invention; and

FIG. 16 is a front view of one embodiment of forming rollers that may beemployed in accordance with the present invention.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentinvention.

Generally speaking, the present invention is directed to an umbilicalfor the transfer of fluids and/or electric current/signals, particularlybetween the sea surface and equipment deployed on the sea bed (e.g., indeep waters). The umbilical contains a plurality of elongated umbilicalelements (e.g., two or more), such as a channel element, fluid pipe,electric conductor/wire (e.g., optic fiber cable), armoring wire, etc.,enclosed within an outer sheath (e.g., plastic sheath). The umbilicalalso contains at least one reinforcing rod formed from a plurality ofunidirectionally aligned fiber rovings embedded within a thermoplasticpolymer matrix. The present inventors have discovered that the degree towhich the rovings are impregnated with the thermoplastic polymer matrixcan be significantly improved through selective control over theimpregnation process, and also through control over the degree ofcompression imparted to the rovings during formation and shaping of therod, as well as the calibration of the final rod geometry. Such a wellimpregnated rod has a very small void fraction, which leads to excellentstrength properties for reinforcing the umbilical elements.

The particular configuration, arrangement, and number of umbilicalelements are not critical and may vary as is known in the art. Referringto FIG. 2, for example, one particular embodiment of an umbilical 600 isshown that contains a central portion 609, which may be formed from asteel pipe, rubber sheath, metallic strand, metallic strandover-sheathed with a thermoplastic material, etc. One or more innerchannel elements 603 (e.g., polyvinylchloride), electricconductors/wires 606 (e.g., optic fiber cables), and/or fluid pipes 604(e.g., steel) may be concentrically disposed about the central portion609. For example, such umbilical elements may be wound helically aroundthe central portion 609 using a helix machine as is known in the art.The umbilical 600 may also contain conventional strength elements 608,such as those made from steel rope or armoring wires. A filler 610(e.g., foam or thermoplastic material) may be arranged at least partlyaround and between two or more of the umbilical elements. An outersheath 601 (e.g., polyethylene) also typically encloses the umbilicalelements.

The reinforcing rod of the present invention may be incorporated intothe umbilical in any desired manner, such as individually or in the formof bundles. In the embodiment illustrated in FIG. 2, a bundle ofreinforcing rods 607 is disposed within the central portion 609 toprovide enhanced strength to the umbilical 600. At least one, butpreferably all of the rods 607 are formed from a continuousfiber-reinforced thermoplastic polymer matrix in accordance with thepresent invention. Of course, the rods need not be contained within thecentral portion of the umbilical. Referring to FIG. 3, for example,another embodiment of an umbilical 700 is shown that contains a bundleof rods 707 located about a periphery of the umbilical. The umbilical700 may also contain a central portion 709, which is either free of rodsas shown or contains a plurality of rods as illustrated in FIG. 2. Theumbilical 700 may also contain one or more inner channel elements 703,electric conductors/wires 706, fluid pipes 704, filler 710, and/or outersheath 701. In the embodiments referenced above, the reinforcing rodsare generally provided in the form of a bundle. However, individual rodsmay also be employed. Referring to FIG. 4, for example, one embodimentof an umbilical 800 is shown that contains one or more channel elements803, pipes 804, and/or electrical conductors/wires 806. The umbilical800 also contains individual rods 807 distributed about the peripheryand/or in the interior of the umbilical 800.

Regardless of the particular manner in which they are incorporated intothe umbilical, the reinforcing rods of the present invention are formedfrom a plurality of unidirectionally aligned fiber rovings embeddedwithin a thermoplastic polymer matrix. As used herein, the term “roving”generally refers to a bundle or tow of individual fibers. The fiberscontained within the roving can be twisted or can be straight. Althoughdifferent fibers can be used in individual or different rovings, it isgenerally desired that each of the rovings contain a single fiber typeto minimize any adverse impact of using material with a differentthermal coefficient of expansion. The continuous fibers employed in therovings possess a high degree of tensile strength relative to theirmass. For example, the ultimate tensile strength of the fibers istypically from about 1,000 to about 15,000 Megapascals (“MPa”), in someembodiments from about 2,000 MPa to about 10,000 MPa, and in someembodiments, from about 3,000 MPa to about 6,000 MPa. Such tensilestrengths may be achieved even though the fibers are of a relativelylight weight, such as a mass per unit length of from about 0.1 to about2 grams per meter, in some embodiments from about 0.4 to about 1.5 gramsper meter. The ratio of tensile strength to mass per unit length maythus be about 1,000 Megapascals per gram per meter (“MPa/g/m”) orgreater, in some embodiments about 4,000 MPa/g/m or greater, and in someembodiments, from about 5,500 to about 20,000 MPa/g/m. Such highstrength fibers may, for instance, be metal fibers, glass fibers (e.g.,E-glass, A-glass, C-glass, D-glass, AR-glass, R-glass, S1-glass,S2-glass, etc.), carbon fibers (e.g., amorphous carbon, graphiticcarbon, or metal-coated carbon, etc.), boron fibers, ceramic fibers(e.g., alumina or silica), aramid fibers (e.g., Kevlar® marketed by E.I. duPont de Nemours, Wilmington, Del.), synthetic organic fibers (e.g.,polyamide, polyethylene, paraphenylene, terephthalamide, polyethyleneterephthalate and polyphenylene sulfide), and various other natural orsynthetic inorganic or organic fibrous materials known for reinforcingthermoplastic compositions. Carbon fibers are particularly suitable foruse as the continuous fibers, which typically have a tensile strength tomass ratio in the range of from about 5,000 to about 7,000 MPa/g/m. Thecontinuous fibers often have a nominal diameter of about 4 to about 35micrometers, and in some embodiments, from about 5 to about 35micrometers. The number of fibers contained in each roving can beconstant or vary from roving to roving. Typically, a roving containsfrom about 1,000 fibers to about 100,000 individual fibers, and in someembodiments, from about 5,000 to about 50,000 fibers.

Any of a variety of thermoplastic polymers may be employed to form thethermoplastic matrix in which the continuous fibers are embedded.Suitable thermoplastic polymers for use in the present invention mayinclude, for instance, polyolefins (e.g., polypropylene,propylene-ethylene copolymers, etc.), polyesters (e.g., polybutyleneterephalate (“PBT”)), polycarbonates, polyamides (e.g., Nylon™),polyether ketones (e.g., polyetherether ketone (“PEEK”)),polyetherimides, polyarylene ketones (e.g., polyphenylene diketone(“PPDK”)), liquid crystal polymers, polyarylene sulfides (e.g.,polyphenylene sulfide (“PPS”), poly(biphenylene sulfide ketone),poly(phenylene sulfide diketone), poly(biphenylene sulfide), etc.),fluoropolymers (e.g., polytetrafluoroethylene-perfluoromethylvinyletherpolymer, perfluoro-alkoxyalkane polymer, petrafluoroethylene polymer,ethylene-tetrafluoroethylene polymer, etc.), polyacetals, polyurethanes,polycarbonates, styrenic polymers (e.g., acrylonitrile butadiene styrene(“ABS”)), and so forth.

The properties of the thermoplastic matrix are generally selected toachieve the desired combination of processability and performance of therod during use. For example, the melt viscosity of the thermoplasticmatrix is generally low enough so that the polymer can adequatelyimpregnate the fibers and become shaped into the rod configuration. Inthis regard, the melt viscosity typically ranges from about 25 to about2,000 Pascal-seconds (“Pa-s”), in some embodiments from 50 about 500Pa-s, and in some embodiments, from about 60 to about 200 Pa-s,determined at the operating conditions used for the thermoplasticpolymer (e.g., about 360° C.). Likewise, when the rod is intended foruse at high temperatures, a thermoplastic polymer is employed that has arelatively high melting temperature. For example, the meltingtemperature of such high temperature polymers may range from about 200°C. to about 500° C., in some embodiments from about 225° C. to about400° C., and in some embodiments, from about 250° C. to about 350° C.

Polyarylene sulfides are particularly suitable for use in the presentinvention as a high temperature matrix with the desired melt viscosity.Polyphenylene sulfide, for example, is a semi-crystalline resin thatgenerally includes repeating monomeric units represented by thefollowing general formula:

These monomeric units typically constitute at least 80 mole %, and insome embodiments, at least 90 mole %, of the recurring units, in thepolymer. It should be understood, however, the polyphenylene sulfide maycontain additional recurring units, such as described in U.S. Pat. No.5,075,381 to Gotoh, et al., which is incorporated herein in its entiretyby reference thereto for all purposes. When employed, such additionalrecurring units typically constitute no more than about 20 mole % of thepolymer. Commercially available high melt viscosity polyphenylenesulfides may include those available from Ticona LLC (Florence,Kentucky) under the trade designation FORTRON®. Such polymers may have amelting temperature of about 285° C. (determined according to ISO11357-1,2,3) and a melt viscosity of from about 260 to about 320Pascal-seconds at 310° C.

According to the present invention, an extrusion device is generallyemployed to impregnate the ravings with the thermoplastic matrix. Amongother things, the extrusion device facilitates the ability of thethermoplastic polymer to be applied to the entire surface of the fibers.The impregnated ravings also have a very low void fraction, which helpsenhance its strength. For instance, the void fraction may be about 6% orless, in some embodiments about 4% or less, in some embodiments about 3%or less, in some embodiments about 2% or less, in some embodiments about1% or less, and in some embodiments, about 0.5% or less. The voidfraction may be measured using techniques well known to those skilled inthe art. For example, the void fraction may be measured using a “resinburn off” test in which samples are placed in an oven (e.g., at 600° C.for 3 hours) to burn out the resin. The mass of the remaining fibers maythen be measured to calculate the weight and volume fractions. Such“burn off” testing may be performed in accordance with ASTM D 2584-08 todetermine the weights of the fibers and the thermoplastic matrix, whichmay then be used to calculate the “void fraction” based on the followingequations:

V _(f)=100*(ρ_(t)−ρ_(c))/ρ_(t)

where,

V_(f) is the void fraction as a percentage;

ρ_(c) is the density of the composite as measured using knowntechniques, such as with a liquid or gas pycnometer (e.g., heliumpycnometer);

ρ_(t) is the theoretical density of the composite as is determined bythe following equation:

ρ_(t)=1/[W _(f) /p _(f) +W _(m)/ρ_(m)]

ρ_(m) is the density of the thermoplastic matrix (e.g., at theappropriate crystallinity);

ρ_(f) is the density of the fibers;

W_(f) is the weight fraction of the fibers; and

W_(m) is the weight fraction of the thermoplastic matrix.

Alternatively, the void fraction may be determined by chemicallydissolving the resin in accordance with ASTM D 3171-09. The “burn off”and “dissolution” methods are particularly suitable for glass fibers,which are generally resistant to melting and chemical dissolution. Inother cases, however, the void fraction may be indirectly calculatedbased on the densities of the thermoplastic polymer, fibers, and ribbon(or tape) in accordance with ASTM D 2734-09 (Method A), where thedensities may be determined ASTM D792-08 Method A. Of course, the voidfraction can also be estimated using conventional microscopy equipment,or through the use of computed tomography (CT) scan equipment, such as aMetrotom 1500 (2k×2k) high resolution detector.

Referring to FIG. 7, one embodiment of such an extrusion device isshown. More particularly, the apparatus includes an extruder 120containing a screw shaft 124 mounted inside a barrel 122. A heater 130(e.g., electrical resistance heater) is mounted outside the barrel 122.During use, a thermoplastic polymer feedstock 127 is supplied to theextruder 120 through a hopper 126. The thermoplastic feedstock 127 isconveyed inside the barrel 122 by the screw shaft 124 and heated byfrictional forces inside the barrel 122 and by the heater 130. Uponbeing heated, the feedstock 127 exits the barrel 122 through a barrelflange 128 and enters a die flange 132 of an impregnation die 150.

A continuous fiber roving 142 or a plurality of continuous fiber rovings142 are supplied from a reel or reels 144 to die 150. The rovings 142are generally kept apart a certain distance before impregnation, such asat least about 4 millimeters, and in some embodiments, at least about 5millimeters. The feedstock 127 may further be heated inside the die byheaters 133 mounted in or around the die 150. The die is generallyoperated at temperatures that are sufficient to cause melting andimpregnation of the thermoplastic polymer. Typically, the operationtemperatures of the die is higher than the melt temperature of thethermoplastic polymer, such as at temperatures from about 200° C. toabout 450° C. When processed in this manner, the continuous fiberrovings 142 become embedded in the polymer matrix, which may be a resin214 (FIG. 8) processed from the feedstock 127. The mixture is thenextruded from the impregnation die 150 to create an extrudate 152.

A pressure sensor 137 (FIG. 8) senses the pressure near the impregnationdie 150 to allow control to be exerted over the rate of extrusion bycontrolling the rotational speed of the screw shaft 124, or the federateof the feeder. That is, the pressure sensor 137 is positioned near theimpregnation die 150 so that the extruder 120 can be operated to delivera correct amount of resin 214 for interaction with the fiber rovings142. After leaving the impregnation die 150, the extrudate 152, orimpregnated fiber rovings 142, may enter an optional pre-shaping, orguiding section (not shown) before entering a nip formed between twoadjacent rollers 190. Although optional, the rollers 190 can help toconsolidate the extrudate 152 into the form of a ribbon, as well asenhance fiber impregnation and squeeze out any excess voids. In additionto the rollers 190, other shaping devices may also be employed, such asa die system. The resulting consolidated ribbon 156 is pulled by tracks162 and 164 mounted on rollers. The tracks 162 and 164 also pull theextrudate 152 from the impregnation die 150 and through the rollers 190.If desired, the consolidated ribbon 156 may be wound up at a section171. Generally speaking, the ribbons are relatively thin and typicallyhave a thickness of from about 0.05 to about 1 millimeter, in someembodiments from about 0.1 to about 0.8 millimeters, and in someembodiments, from about 0.2 to about 0.4 millimeters.

Within the impregnation die, it is generally desired that the ravings142 are traversed through an impregnation zone 250 to impregnate therovings with the polymer resin 214. In the impregnation zone 250, thepolymer resin may be forced generally transversely through the rovingsby shear and pressure created in the impregnation zone 250, whichsignificantly enhances the degree of impregnation. This is particularlyuseful when forming a composite from ribbons of a high fiber content,such as about 35% weight fraction (“Wf”) or more, and in someembodiments, from about 40% W for more. Typically, the die 150 willinclude a plurality of contact surfaces 252, such as for example atleast 2, at least 3, from 4 to 7, from 2 to 20, from 2 to 30, from 2 to40, from 2 to 50, or more contact surfaces 252, to create a sufficientdegree of penetration and pressure on the rovings 142. Although theirparticular form may vary, the contact surfaces 252 typically possess acurvilinear surface, such as a curved lobe, rod, etc. The contactsurfaces 252 are also typically made of a metal material.

FIG. 8 shows a cross-sectional view of an impregnation die 150. Asshown, the impregnation die 150 includes a manifold assembly 220, a gatepassage 270, and an impregnation zone 250. The manifold assembly 220 isprovided for flowing the polymer resin 214 therethrough. For example,the manifold assembly 220 may include a channel 222 or a plurality ofchannels 222. The resin 214 provided to the impregnation die 150 mayflow through the channels 222.

As shown in FIG. 9, some portions of the channels 222 may becurvilinear, and in exemplary embodiments, the channels 222 have asymmetrical orientation along a central axis 224. Further, in someembodiments, the channels may be a plurality of branched runners 222,which may include first branched runner group 232, second group 234,third group 236, and, if desired, more branched runner groups. Eachgroup may include 2, 3, 4 or more runners 222 branching off from runners222 in the preceding group, or from an initial channel 222.

The branched runners 222 and the symmetrical orientation thereofgenerally evenly distribute the resin 214, such that the flow of resin214 exiting the manifold assembly 220 and coating the rovings 142 issubstantially uniformly distributed on the rovings 142. This desirablyallows for generally uniform impregnation of the rovings 142.

Further, the manifold assembly 220 may in some embodiments define anoutlet region 242, which generally encompasses at least a downstreamportion of the channels or runners 222 from which the resin 214 exits.In some embodiments, at least a portion of the channels or runners 222disposed in the outlet region 242 have an increasing area in a flowdirection 244 of the resin 214. The increasing area allows for diffusionand further distribution of the resin 214 as the resin 214 flows throughthe manifold assembly 220, which further allows for substantiallyuniform distribution of the resin 214 on the rovings 142.

As further illustrated in FIGS. 8 and 9, after flowing through themanifold assembly 220, the resin 214 may flow through gate passage 270.Gate passage 270 is positioned between the manifold assembly 220 and theimpregnation zone 250, and is provided for flowing the resin 214 fromthe manifold assembly 220 such that the resin 214 coats the rovings 142.Thus, resin 214 exiting the manifold assembly 220, such as throughoutlet region 242, may enter gate passage 270 and flow therethrough, asshown.

Upon exiting the manifold assembly 220 and the gate passage 270 of thedie 150 as shown in FIG. 8, the resin 214 contacts the ravings 142 beingtraversed through the die 150. As discussed above, the resin 214 maysubstantially uniformly coat the rovings 142, due to distribution of theresin 214 in the manifold assembly 220 and the gate passage 270.Further, in some embodiments, the resin 214 may impinge on an uppersurface of each of the rovings 142, or on a lower surface of each of therovings 142, or on both an upper and lower surface of each of therovings 142. Initial impingement on the ravings 142 provides for furtherimpregnation of the rovings 142 with the resin 214.

As shown in FIG. 8, the coated rovings 142 are traversed in rundirection 282 through impregnation zone 250, which is configured toimpregnate the rovings 142 with the resin 214. For example, as shown inFIGS. 8 and 10, the rovings 142 are traversed over contact surfaces 252in the impregnation zone. Impingement of the rovings 142 on the contactsurface 252 creates shear and pressure sufficient to impregnate theravings 142 with the resin 214 coating the rovings 142.

In some embodiments, as shown in FIG. 8, the impregnation zone 250 isdefined between two spaced apart opposing plates 256 and 258. Firstplate 256 defines a first inner surface 257, while second plate 258defines a second inner surface 259. The contact surfaces 252 may bedefined on or extend from both the first and second inner surfaces 257and 259, or only one of the first and second inner surfaces 257 and 259.FIG. 10 illustrates the second plate 258 and the various contactsurfaces thereon that form at least a portion of the impregnation zone250 according to these embodiments. In exemplary embodiments, as shownin FIG. 8, the contact surfaces 252 may be defined alternately on thefirst and second surfaces 257 and 259 such that the rovings alternatelyimpinge on contact surfaces 252 on the first and second surfaces 257 and259. Thus, the rovings 142 may pass contact surfaces 252 in a waveform,tortuous or sinusoidual-type pathway, which enhances shear.

Angle 254 at which the rovings 142 traverse the contact surfaces 252 maybe generally high enough to enhance shear, but not so high to causeexcessive forces that will break the fibers. Thus, for example, theangle 254 may be in the range between approximately 1° and approximately30°, and in some embodiments, between approximately 5° and approximately25°.

In alternative embodiments, the impregnation zone 250 may include aplurality of pins (not shown), each pin having a contact surface 252.The pins may be static, freely rotational, or rotationally driven. Infurther alternative embodiments, the contact surfaces 252 andimpregnation zone 250 may comprise any suitable shapes and/or structuresfor impregnating the rovings 142 with the resin 214 as desired orrequired.

To further facilitate impregnation of the rovings 142, they may also bekept under tension while present within the impregnation die. Thetension may, for example, range from about 5 to about 300 Newtons, insome embodiments from about 50 to about 250 Newtons, and in someembodiments, from about 100 to about 200 Newtons per roving 142 or towof fibers.

As shown in FIG. 8, in some embodiments, a land zone 280 may bepositioned downstream of the impregnation zone 250 in run direction 282of the rovings 142. The rovings 142 may traverse through the land zone280 before exiting the die 150. As further shown in FIG. 8, in someembodiments, a faceplate 290 may adjoin the impregnation zone 250.Faceplate 290 is generally configured to meter excess resin 214 from therovings 142. Thus, apertures in the faceplate 290, through which therovings 142 traverse, may be sized such that when the rovings 142 aretraversed therethrough, the size of the apertures causes excess resin214 to be removed from the rovings 142.

The impregnation die shown and described above is but one of variouspossible configurations that may be employed in the present invention.In alternative embodiments, for example, the rovings may be introducedinto a crosshead die that is positioned at an angle relative to thedirection of flow of the polymer melt. As the ravings move through thecrosshead die and reach the point where the polymer exits from anextruder barrel, the polymer is forced into contact with the rovings.Examples of such a crosshead die extruder are described, for instance,in U.S. Pat. Nos. 3,993,726 to Moyer; 4,588,538 to Chung, et al.;5,277,566 to Augustin, et al.; and 5,658,513 to Amaike, et al., whichare incorporated herein in their entirety by reference thereto for allpurposes. It should also be understood that any other extruder designmay also be employed, such as a twin screw extruder. Still further,other components may also be optionally employed to assist in theimpregnation of the fibers. For example, a “gas jet” assembly may beemployed in certain embodiments to help uniformly spread a roving ofindividual fibers, which may each contain up to as many as 24,000fibers, across the entire width of the merged tow. This helps achieveuniform distribution of strength properties. Such an assembly mayinclude a supply of compressed air or another gas that impinges in agenerally perpendicular fashion on the moving rovings that pass acrossthe exit ports. The spread rovings may then be introduced into a die forimpregnation, such as described above.

Regardless of the technique employed, the continuous fibers are orientedin the longitudinal direction (the machine direction “A” of the systemof FIG. 7) to enhance tensile strength. Besides fiber orientation, otheraspects of the pultrusion process are also controlled to achieve thedesired strength. For example, a relatively high percentage ofcontinuous fibers are employed in the consolidated ribbon to provideenhanced strength properties. For instance, continuous fibers typicallyconstitute from about 25 wt. % to about 80 wt. %, in some embodimentsfrom about 30 wt. % to about 75 wt. %, and in some embodiments, fromabout 35 wt. % to about 60 wt. % of the ribbon. Likewise, thermoplasticpolymer(s) typically constitute from about 20 wt. % to about 75 wt. %,in some embodiments from about 25 wt. % to about 70 wt. %, and in someembodiments, from about 40 wt. % to about 65 wt. % of the ribbon. Thepercentage of the fibers and thermoplastic matrix in the final rod mayalso be within the ranges noted above.

As noted above, the ravings may be consolidated into the form of one ormore ribbons before being shaped into the desired rod configuration.When such a ribbon is subsequently compressed, the ravings can becomedistributed in a generally symmetrical manner about a longitudinalcenter of the rod. Such symmetrical distribution enhances theconsistency of the strength properties (e.g., flexural modulus, ultimatetensile strength, etc.) over the entire length of the rod. Whenemployed, the number of consolidated ribbons used to form the rod willvary based on the desired thickness and/or cross-sectional area andstrength of the rod, as well as the nature of the ribbons themselves. Inmost cases, however, the number of ribbons is from 1 to 15, and in someembodiments, from 2 to 5. The number of rovings employed in each ribbonmay likewise vary. Typically, however, a ribbon will contain from 2 to10 rovings, and in some embodiments, from 3 to 5 rovings. To helpachieve the symmetric distribution of the ravings in the final rod, itis generally desired that they are spaced apart approximately the samedistance from each other within the ribbon. Referring to FIG. 5, forexample, one embodiment of a consolidated ribbon 4 is shown thatcontains three (3) rovings 5 spaced equidistant from each other in the−x direction. In other embodiments, however, it may be desired that therovings are combined, such that the fibers of the rovings are generallyevenly distributed throughout the ribbon 4. In these embodiments, therovings may be generally indistinguishable from each other. Referring toFIG. 6, for example, one embodiment of a consolidated ribbon 4 is shownthat contains rovings that are combined such that the fibers aregenerally evenly distributed.

The specific manner in which the rovings are shaped is also carefullycontrolled to ensure that rod can be formed with an adequate degree ofcompression and strength properties. Referring to FIG. 11, for example,one particular embodiment of a system and method for forming a rod areshown. In this embodiment, two ribbons 12 are initially provided in awound package on a creel 20. The creel 20 may be an unreeling creel thatincludes a frame provided with horizontal rotating spindles 22, eachsupporting a package. A pay-out creel may also be employed, particularlyif desired to induce a twist into the fibers, such as when using rawfibers in a one-step configuration. It should also be understood thatthe ribbons may also be formed in-line with the formation of the rod. Inone embodiment, for example, the extrudate 152 exiting the impregnationdie 150 from FIG. 7 may be directly supplied to the system used to forma rod. A tension-regulating device 40 may also be employed to helpcontrol the degree of tension in the ribbons 12. The device 40 mayinclude inlet plate 30 that lies in a vertical plane parallel to therotating spindles 22 of the creel 20 and/or perpendicular to theincoming ribbons. The tension-regulating device 40 may containcylindrical bars 41 arranged in a staggered configuration so that theribbons 12 passes over and under these bars to define a wave pattern.The height of the bars can be adjusted to modify the amplitude of thewave pattern and control tension.

The ribbons 12 may be heated in an oven 45 before entering theconsolidation die. Heating may be conducted using any known type ofoven, as in an infrared oven, convection oven, etc. During heating, thefibers in the ribbon are unidirectionally oriented to optimize theexposure to the heat and maintain even heat across the entire ribbon.The temperature to which the ribbons 12 are heated is generally highenough to soften the thermoplastic polymer to an extent that the ribbonscan bond together. However, the temperature is not so high as to destroythe integrity of the material. The temperature may, for example, rangefrom about 100° C. to about 500° C., in some embodiments from about 200°C. to about 400° C., and in some embodiments, from about 250° C. toabout 350° C. In one particular embodiment, for example, polyphenylenesulfide (“PPS”) is used as the polymer, and the ribbons are heated to orabove the melting point of PPS, which is about 285° C.

Upon being heated, the ribbons 12 are provided to a consolidation die 50that compresses them together into a preform 14, as well as aligns andforms the initial shape of the rod. As shown generally in FIG. 11, forexample, the ribbons 12 are guided through a flow passage 51 of the die50 in a direction “A” from an inlet 53 to an outlet 55. The passage 51may have any of a variety of shapes and/or sizes to achieve the rodconfiguration. For example, the channel and rod configuration may becircular, elliptical, parabolic, etc. Within the die 50, the ribbons aregenerally maintained at a temperature at or above the melting point ofthe thermoplastic matrix used in the ribbon to ensure adequateconsolidation.

The desired heating, compression, and shaping of the ribbons 12 may beaccomplished through the use of a die 50 having one or multiplesections. For instance, although not shown in detail herein, theconsolidation die 50 may possess multiple sections that functiontogether to compress and shape the ribbons 12 into the desiredconfiguration. For instance, a first section of the passage 51 may be atapered zone that initially shapes the material as it flows from intothe die 50. The tapered zone generally possesses a cross-sectional areathat is larger at its inlet than at its outlet. For example, thecross-sectional area of the passage 51 at the inlet of the tapered zonemay be about 2% or more, in some embodiments about 5% or more, and insome embodiments, from about 10% to about 20% greater than thecross-sectional area at the outlet of the tapered zone. Regardless, thecross-sectional of the flow passage typically changes gradually andsmoothly within the tapered zone so that a balanced flow of thecomposite material through the die can be maintained. A shaping zone mayalso follow the tapered zone that compresses the material and provides agenerally homogeneous flow therethrough. The shaping zone may alsopre-shape the material into an intermediate shape that is similar tothat of the rod, but typically of a larger cross-sectional area to allowfor expansion of the thermoplastic polymer while heated to minimize therisk of backup within the die 50. The shaping zone could also includeone or more surface features that impart a directional change to thepreform. The directional change forces the material to be redistributedresulting in a more even distribution of the fiber/resin in the finalshape. This also reduces the risk of dead spots in the die that cancause burning of the resin. For example, the cross-sectional area of thepassage 51 at the shaping zone may be about 2% or more, in someembodiments about 5% or more, and in some embodiments, from about 10% toabout 20% greater than the width of the preform 14. A die land may alsofollow the shaping zone to serve as an outlet for the passage 51. Theshaping zone, tapered zone, and/or die land may be heated to atemperature at or above that of the glass transition temperature ormelting point of the thermoplastic matrix.

If desired, a second die 60 (e.g., calibration die) may also be employedthat compresses the preform 14 into the final shape of the rod. Whenemployed, it is sometimes desired that the preform 14 is allowed to coolbriefly after exiting the consolidation die 50 and before entering theoptional second die 60. This allows the consolidated preform 14 toretain its initial shape before progressing further through the system.Typically, cooling reduces the temperature of the exterior of the rodbelow the melting point temperature of the thermoplastic matrix tominimize and substantially prevent the occurrence of melt fracture onthe exterior surface of the rod. The internal section of the rod,however, may remain molten to ensure compression when the rod enters thecalibration die body. Such cooling may be accomplished by simplyexposing the preform 14 to the ambient atmosphere (e.g., roomtemperature) or through the use of active cooling techniques (e.g.,water bath or air cooling) as is known in the art. In one embodiment,for example, air is blown onto the preform 14 (e.g., with an air ring).The cooling between these stages, however, generally occurs over a smallperiod of time to ensure that the preform 14 is still soft enough to befurther shaped. For example, after exiting the consolidation die 50, thepreform 14 may be exposed to the ambient environment for only from about1 to about 20 seconds, and in some embodiments, from about 2 to about 10seconds, before entering the second die 60. Within the die 60, thepreform is generally kept at a temperature below the melting point ofthe thermoplastic matrix used in the ribbon so that the shape of the rodcan be maintained. Although referred to above as single dies, it shouldbe understood that the dies 50 and 60 may in fact be formed frommultiple individual dies (e.g., face plate dies).

Thus, in some embodiments, multiple individual dies 60 may be utilizedto gradually shape the material into the desired configuration. The dies60 are placed in series, and provide for gradual decreases in thedimensions of the material. Such gradual decreases allow for shrinkageduring and between the various steps.

For example, as shown in FIGS. 13 through 15, a first die 60 may includeone or more inlet 62 and corresponding outlets 64, as shown. Any numberof inlets 62 and corresponding outlets 64 may be included in a die 60,such as four as shown, one, two, three, five, six, or more. An inlet 62in some embodiments may be generally oval or circle shaped. In otherembodiments, the inlet 62 may have a curved rectangular shape, i.e. arectangular shape with curved corners or a rectangular shape withstraight longer sidewalls and curved shorter sidewalls. Further, anoutlet 64 may be generally oval or circle shaped, or may have a curvedrectangular shape. In some embodiments wherein an oval shaped inlet isutilized, the inlet 62 may have a major axis length 66 to minor axislength 68 ratio in a range between approximately 3 to 1 andapproximately 5 to 1. In some embodiments wherein an oval or circularshaped inlet is utilized, the outlet 64 may have a major axis length 66to minor axis length 68 ratio in a range between approximately 1 to 1and approximately 3 to 1. In embodiments wherein a curved rectangularshape is utilized, the inlet and outlet may have major axis length 66 tominor axis length 66 ratios (aspect ratios) between approximately 2 to 1and approximately 7 to 1, with the outlet 64 ratio being less than theinlet 62 ratio.

In further embodiments, the cross-sectional area of an inlet 62 and thecross-sectional area of a corresponding outlet 64 of the first die 60may have a ratio in a range between approximately 1.5 to 1 and 6 to 1.

The first die 60 thus provides a generally smooth transformation ofpolymer impregnated fiber material to a shape that is relatively similarto a final shape of the resulting rod, which in exemplary embodimentshas a circular or oval shaped cross-section. Subsequent dies, such as asecond die 60 and third die 60 as shown in FIG. 13, may provide forfurther gradual decreases and/or changes in the dimensions of thematerial, such that the shape of the material is converted to a finalcross-sectional shape of the rod. These subsequent dies 60 may bothshape and cool the material. For example, in some embodiments, eachsubsequent die 60 may be maintained at a lower temperature than theprevious dies. In exemplary embodiments, all dies 60 are maintained attemperatures that are higher than a softening point temperature for thematerial.

In further exemplary embodiments, dies 60 having relatively long landlengths 69 may be desired, due to for example desires for proper coolingand solidification, which are critical in achieving a desired rod shapeand size. Relatively long land lengths 69 reduce stresses and providesmooth transformations to desired shapes and sizes, and with minimalvoid fraction and bow characteristics. In some embodiments, for example,a ratio of land length 69 at an outlet 64 to major axis length 66 at theoutlet 64 for a die 60 may be in the range between approximately 0 andapproximately 20, such as between approximately 2 and approximately 6.

The use of calibration dies 60 according to the present disclosureprovides for gradual changes in material cross-section, as discussed.These gradual changes may in exemplary embodiments ensure that theresulting product, such as a rod or other suitable product, has agenerally uniform fiber distribution with relatively minimal voidfraction.

It should be understood that any suitable number of dies 60 may beutilized to gradually form the material into a profile having anysuitable cross-sectional shape, as desired or required by variousapplications.

In addition to the use of one or more dies, other mechanisms may also beemployed to help compress the preform 14 into the shape of a rod. Forexample, forming rollers 90, as shown in FIG. 16, may be employedbetween the consolidation die 50 and the calibration die 60, between thevarious calibration dies 60, and/or after the calibration dies 60 tofurther compress the preform 14 before it is converted into its finalshape. The rollers may have any configuration, such as pinch rollers,overlapping rollers, etc., and may be vertical as shown or horizontalrollers. Depending on the roller 90 configuration, the surfaces of therollers 90 may be machined to impart the dimensions of the finalproduct, such as the rod, profile, or other suitable product, to thepreform 14. In exemplary embodiment, the pressure of the rollers 90should be adjustable to optimize the quality of the final product.

The rollers 90 in exemplary embodiments, such as at least the portionscontacting the material, may have generally smooth surfaces. Forexample, relatively hard, polished surfaces are desired in manyembodiments. For example, the surface of the rollers may be formed froma relatively smooth chrome or other suitable material. This allows therollers 90 to manipulate the preform 14 without damaging or undesirablyaltering the preform 14. For example, such surfaces may prevent thematerial from sticking to the rollers, and the rollers may impart smoothsurfaces onto the materials.

In some embodiments, the temperature of the rollers 90 is controlled.This may be accomplished by heating of the rollers 90 themselves, or byplacing the rollers 90 in a temperature controlled environment.

Further, in some embodiments, surface features 92 may be provided on therollers 90. The surface features 92 may guide and/or control the preform14 in one or more directions as it is passed through the rollers. Forexample, surface features 92 may be provided to prevent the preform 14from folding over on itself as it is passed through the rollers 90.Thus, the surface features 92 may guide and control deformation of thepreform 14 in the cross-machine direction relative to the machinedirection A as well as in the vertical direction relative to the machinedirection A. The preform 14 may thus be pushed together in thecross-machine direction, rather than folded over on itself, as it ispassed through the rollers 90 in the machine direction A.

In some embodiments, tension regulation devices may be provided incommunication with the rollers. These devices may be utilized with therollers to apply tension to the preform 14 in the machine direction,cross-machine direction, and/or vertical direction to further guideand/or control the preform.

If desired, the resulting rod may optionally be applied with a cappinglayer to protect it from environmental conditions or to improve wearresistance. Referring again to FIG. 11, for example, such a cappinglayer may be applied via an extruder oriented at any desired angle tointroduce a thermoplastic resin into a capping die 72. Suitablethermoplastic polymers for this purpose may include, for instance,polyolefins (e.g., polypropylene, propylene-ethylene copolymers, etc.),polyesters (e.g., polybutylene terephalate (“PBT”)), polycarbonates,polyamides (e.g., Nylon™), polyether ketones (e.g., polyetheretherketone (“PEEK”)), polyetherimides, polyarylene ketones (e.g.,polyphenylene diketone (“PPDK”)), liquid crystal polymers, polyarylenesulfides (e.g., polyphenylene sulfide (“PPS”), poly(biphenylene sulfideketone), poly(phenylene sulfide diketone), poly(biphenylene sulfide),etc.), fluoropolymers (e.g.,polytetrafluoroethylene-perfluoromethylvinylether polymer,perfluoro-alkoxyalkane polymer, petrafluoroethylene polymer,ethylene-tetrafluoroethylene polymer, etc.), polyacetals, polyurethanes,polycarbonates, styrenic polymers (e.g., acrylonitrile butadiene styrene(“ABS”)), acrylic polymers, polyvinyl chloride (PVC), etc. Particularlysuitable capping layer materials may include polyketone (e.g.,polyetherether ketone (“PEEK”)), polysulfide (e.g., polyarylenesulfide), or a mixture thereof.

Although not required, the capping layer may be generally free ofcontinuous fibers. That is, the capping layer contains less than about10 wt. % of continuous fibers, in some embodiments about 5 wt. % or lessof continuous fibers, and in some embodiments, about 1 wt. % or less ofcontinuous fibers (e.g., 0 wt. %). Nevertheless, the capping layer maycontain other additives for improving the final properties of the rod.Additive materials employed at this stage may include those that are notsuitable for incorporating into the continuous fiber material. Forinstance, it may be desirable to add pigments to reduce finishing labor,or it may be desirable to add flame retardant agents to enhance theflame retarding features of the rod. Because many additive materials areheat sensitive, an excessive amount of heat may cause them to decomposeand produce volatile gases. Therefore, if a heat sensitive additivematerial is extruded with an impregnation resin under high heatingconditions, the result may be a complete degradation of the additivematerial. Additive materials may include, for instance, mineralreinforcing agents, lubricants, flame retardants, blowing agents,foaming agents, ultraviolet light resistant agents, thermal stabilizers,pigments, and combinations thereof. Suitable mineral reinforcing agentsmay include, for instance, calcium carbonate, silica, mica, clays, talc,calcium silicate, graphite, calcium silicate, alumina trihydrate, bariumferrite, and combinations thereof.

While not shown in detail herein, the capping die 72 may include variousfeatures known in the art to help achieve the desired application of thecapping layer. For instance, the capping die 72 may include an entranceguide that aligns the incoming rod. The capping die may also include aheating mechanism (e.g., heated plate) that pre-heats the rod beforeapplication of the capping layer to help ensure adequate bonding.Following capping, the shaped part 15 is then finally cooled using acooling system 80 as is known in the art. The cooling system 80 may, forinstance, be a sizing system that includes one or more blocks (e.g.,aluminum blocks) that completely encapsulate the rod while a vacuumpulls the hot shape out against its walls as it cools. A cooling mediummay be supplied to the sizer, such as air or water, to solidify the rodin the correct shape.

Even if a sizing system is not employed, it is generally desired to coolthe rod after it exits the capping die (or the consolidation orcalibration die if capping is not applied). Cooling may occur using anytechnique known in the art, such a water tank, cool air stream or airjet, cooling jacket, an internal cooling channel, cooling fluidcirculation channels, etc. Regardless, the temperature at which thematerial is cooled is usually controlled to achieve optimal mechanicalproperties, part dimensional tolerances, good processing, and anaesthetically pleasing composite. For instance, if the temperature ofthe cooling station is too high, the material might swell in the tooland interrupt the process. For semi-crystalline materials, too low of atemperature can likewise cause the material to cool down too rapidly andnot allow complete crystallization, thereby jeopardizing the mechanicaland chemical resistance properties of the composite. Multiple coolingdie sections with independent temperature control can be utilized toimpart the optimal balance of processing and performance attributes. Inone particular embodiment, for example, a water tank is employed that iskept at a temperature of from about 0° C. to about 30° C., in someembodiments from about 1° C. to about 20° C., and in some embodiments,from about 2° C. to about 15° C.

If desired, one or more sizing blocks (not shown) may also be employed,such as after capping. Such blocks contain openings that are cut to theexact rod shape, graduated from oversized at first to the final rodshape. As the rod passes therethrough, any tendency for it to move orsag is counteracted, and it is pushed back (repeatedly) to its correctshape. Once sized, the rod may be cut to the desired length at a cuttingstation (not shown), such as with a cut-off saw capable of performingcross-sectional cuts or the rod can be wound on a reel in a continuousprocess. The length of rod will then be limited to the length of thefiber tow.

As will be appreciated, the temperature of the rod as it advancesthrough any section of the system of the present invention may becontrolled to yield optimal manufacturing and desired final compositeproperties. Any or all of the assembly sections may be temperaturecontrolled utilizing electrical cartridge heaters, circulated fluidcooling, etc., or any other temperature controlling device known tothose skilled in the art.

Referring again to FIG. 11, a pulling device 82 is positioned downstreamfrom the cooling system 80 that pulls the finished rod 16 through thesystem for final sizing of the composite. The pulling device 82 may beany device capable of pulling the rod through the process system at adesired rate. Typical pulling devices include, for example, caterpillarpullers and reciprocating pullers.

One embodiment of the rod formed from the method described above isshown in more detail in FIG. 12 as element 516. As illustrated, the rod516 has a generally circular shape and includes a core 514 formed fromone or more consolidated ribbons. By “generally circular”, it isgenerally meant that the aspect ratio of the rod (height divided by thewidth) is typically from about 1.0 to about 1.5, and in someembodiments, about 1.0. Due to the selective control over the processused to impregnate the rovings and form a consolidated ribbon, as wellthe process for compressing and shaping the ribbon, the rod is able topossess a relatively even distribution of the thermoplastic matrixacross along its entire length. This also means that the continuousfibers are distributed in a generally uniform manner about alongitudinal central axis “L” of the rod 516. As shown in FIG. 12, forexample, the core 514 includes continuous fibers 526 embedded within athermoplastic matrix 528. The fibers 526 are distributed generallyuniformly about the longitudinal axis “L.” It should be understood thatonly a few fibers are shown in FIG. 12, and that the rod will typicallycontain a substantially greater number of uniformly distributed fibers.

A capping layer 519 also extends around the perimeter of the core 514and defines an external surface of the rod 516. The cross-sectionalthickness (“T”) of the rod 514 may be strategically selected to helpachieve a particular strength. For example, the rod 514 may have athickness (e.g., diameter) of from about 0.1 to about 40 millimeters, insome embodiments from about 0.5 to about 30 millimeters, and in someembodiments, from about 1 to about 10 millimeters. The thickness of thecapping layer 519 depends on the intended function of the part, but istypically from about 0.01 to about 10 millimeters, and in someembodiments, from about 0.02 to about 5 millimeters. Regardless, thetotal cross-sectional thickness or height of the rod typically rangesfrom about of from about 0.1 to about 50 millimeters, in someembodiments from about 0.5 to about 40 millimeters, and in someembodiments, from about 1 to about 20 millimeters. While the rod may besubstantially continuous in length, the length of the rod is oftenpractically limited by the spool onto which it will be wound and storedor the length of the continuous fibers. For example, the length oftenranges from about 1000 to about 5000 meters, although even greaterlengths are certainly possible.

A capping layer 519 also extends around the perimeter of the core 514and defines an external surface of the rod 516. The cross-sectionalthickness (“T”) of the core 514 may be strategically selected to helpachieve a particular strength for the rod. For example, the core 514 mayhave a thickness (e.g., diameter) of from about 0.1 to about 40millimeters, in some embodiments from about 0.5 to about 30 millimeters,and in some embodiments, from about 1 to about 10 millimeters. Thethickness of the capping layer 519 depends on the intended function ofthe part, but is typically from about 0.01 to about 10 millimeters, andin some embodiments, from about 0.02 to about 5 millimeters. The totalcross-sectional thickness or height of the rod 516 may also range fromabout of from about 0.1 to about 50 millimeters, in some embodimentsfrom about 0.5 to about 40 millimeters, and in some embodiments, fromabout 1 to about 20 millimeters. While the rod may be substantiallycontinuous in length, the length of the rod is often practically limitedby the spool onto which it will be wound and stored. For example, thelength often ranges from about 1000 to about 5000 meters, although evengreater lengths are certainly possible.

Through control over the various parameters mentioned above, rods havinga very high strength may be formed. For example, the rods may exhibit arelatively high flexural modulus. The term “flexural modulus” generallyrefers to the ratio of stress to strain in flexural deformation (unitsof force per area), or the tendency for a material to bend. It isdetermined from the slope of a stress-strain curve produced by a “threepoint flexural” test (such as ASTM D790-10, Procedure A), typically atroom temperature. For example, the rod of the present invention mayexhibit a flexural modulus of from about 10 Gigapascals (“GPa”) or more,in some embodiments from about 12 to about 400 GPa, in some embodimentsfrom about 15 to about 200 GPa, and in some embodiments, from about 20to about 150 GPa. Furthermore, the ultimate tensile strength may beabout 300 Megapascals (“MPa”) or more, in some embodiments from about400 MPa to about 5,000 MPa, and in some embodiments, from about 500 MPato about 3,500 MPa. The term “ultimate tensile strength” generallyrefers to the maximum stress that a material can withstand while beingstretched or pulled before necking and is the maximum stress reached ona stress-strain curve produced by a tensile test (such as ASTM D3916-08)at room temperature. The tensile modulus of elasticity may also be about50 GPa or more, in some embodiments from about 70 GPa to about 500 GPa,and in some embodiments, from about 100 GPa to about 300 GPa. The term“tensile modulus of elasticity” generally refers to the ratio of tensilestress over tensile strain and is the slope of a stress-strain curveproduced by a tensile test (such as ASTM 3916-08) at room temperature.Notably, the strength properties of the composite rod referenced abovemay also be maintained over a relatively wide temperature range, such asfrom about −40° C. to about 300° C., and particularly from about 180° C.to 200° C.

Rods made according to the present disclosure may further haverelatively flexural fatigue life, and may exhibit relatively highresidual strength. Flexural fatigue life and residual flexural strengthmay be determined based on a “three point flexural fatigue” test (suchas ASTM D790, typically at room temperature. For example, the rods ofthe present invention may exhibit residual flexural strength after onemillion cycles at 160 Newtons (“N”) or 180 N loads of from about 60kilograms per square inch (“ksi”) to about 115 ksi, in some embodimentsabout 70 ksi to about 115 ksi, and in some embodiments about 95 ksi toabout 115 ksi. Further, the rods may exhibit relatively minimalreductions in flexural strength. For example, rods having void fractionsof about 4% or less, in some embodiments about 3% or less, may exhibitreductions in flexural strength after three point flexural fatiguetesting of about 1% (for example, from a maximum pristine flexuralstrength of about 106 ksi to a maximum residual flexural strength ofabout 105 ksi). Flexural strength may be tested before and after fatiguetesting using, for example, a three point flexural test as discussedabove.

The linear thermal expansion coefficient of the composite rod may be, ona ppm basis per ° C., less than about 5, less than about 4, less thanabout 3, or less than about 2. For instance, the coefficient (ppm/° C.)may be in a range from about −0.25 to about 5; alternatively, from about−0.17 to about 4; alternatively, from about −0.17 to about 3;alternatively, from about −0.17 to about 2; or alternatively, from about0.29 to about 1.18. The temperature range contemplated for this linearthermal expansion coefficient may be generally in the −50° C. to 200° C.range, the 0° C. to 200° C. range, the 0° C. to 175° C. range, or the25° C. to 150° C. range. The linear thermal expansion coefficient ismeasured in the longitudinal direction, i.e., along the length of thefibers.

The composite rod may also exhibit a relatively small “bend radius”,which is the minimum radius that the rod can be bent without breakingand is measured to the inside curvature of the rod. A smaller bendradius means that the rod is more flexible and can be spooled onto asmaller diameter bobbin. This property also makes the rod easier toimplement in processes that currently use metal rods. Due to theimproved process and resulting rod of the present invention, bendradiuses may be achieved that are less than about 40 times the outerdiameter of the rod, in some embodiments from about 1 to about 30 timesthe outer diameter of the rod, and in some embodiments, from about 2 toabout 25 times the outer diameter of the rod, determined at atemperature of about 25° C. For instance, the bend radius may be lessthan about 15 centimeters, in some embodiments from about 0.5 to about10 centimeters, and in some embodiments, from about 1 to about 6centimeters, determined at a temperature of about 25° C.

The composite rod also has a very low void fraction, such as about 6% orless, in some embodiments 3% or less, in some embodiments about 2% orless, in some embodiments about 1% or less, and in some embodiments,about 0.5% or less. The void fraction may be determined in the mannerdescribed above, such as using a “resin burn off” test in accordancewith ASTM D 2584-08 or through the use of computed tomography (CT) scanequipment, such as a Metrotom 1500 (2k×2k) high resolution detector.

As will be appreciated, the particular embodiment described above ismerely exemplary of the numerous designs that are made possible by thepresent invention. Among the various possible rod designs, it should beunderstood that additional layers of material may be employed inaddition to those described above. In certain embodiments, for example,it may be desirable to form a multi-component rod in which one componentis formed from a higher strength material and another component isformed from a lower strength material. Such multi-component rods may beparticularly useful in increasing overall strength without requiring theneed for more expensive high strength materials for the entire rod. Thelower and/or higher strength components may be formed from ribbon(s)that contain continuous fibers embedded within a thermoplastic matrix.

It should be understood that the present invention is by no meanslimited to the embodiments described above. For example, the rods maycontain various other components depending on the desired application.The additional components may be formed from a continuous fiber ribbon,such as described herein, as well as other types of materials. In oneembodiment, for example, the rod may contain a layer of discontinuousfibers (e.g., short fibers, long fibers, etc.) to improve its transversestrength. The discontinuous fibers may be oriented so that at least aportion of the fibers are positioned at an angle relative to thedirection in which the continuous fibers extend.

The rod of the present invention provides various advantages andbenefits especially when used to construct umbilicals. For example, dueto its construction, the rod may be strong, lightweight, and may beeasily processible and compatible with other materials used in theumbilical. The umbilical of the present invention may be employed in awide variety of applications, such as in subsea environments. FIG. 1,for instance, shows one embodiment of an umbilical 900 in a body ofwater 912, which is a connecting vessel 910 with subsea facility 916adjacent the bottom 914 of body of water 912. The vessel 910 and/orsubsea facility 916 may be permanently installed or movable within thebody of water 912. In certain embodiments, the umbilical 900 may beemployed in water having a depth of about 2,500 meters or more, in someembodiments about 4,000 meters or more, and in some embodiments, fromabout 5,000 to about 15,000 meters.

The present disclosure may be better understood with reference to thefollowing examples.

Example 1

Two (2) continuous fiber ribbons were initially formed using anextrusion system as substantially described above. Carbon fiber rovings(Toray T700SC, which contained 12,000 carbon filaments having a tensilestrength of 4,900 MPa and a mass per unit length of 0.8 grams per meter)were employed for the continuous fibers with each individual ribboncontaining 4 ravings. The thermoplastic polymer used to impregnate thefibers was polyphenylene sulfide (“PPS”) (FORTRON® PPS 205, availablefrom Ticona LLC), which has a melting point of about 280° C. Each ribboncontained 50 wt. % carbon fibers and 50 wt. % PPS. The ribbons had athickness of about 0.18 millimeters and a void fraction of less than1.0%. Once formed, the ribbons were then fed to a pultrusion lineoperating at a speed of 20 feet per minute. Before shaping, the ribbonswere heated within an infrared oven (power setting of 305). The heatedribbons were then supplied to a consolidation die having acircular-shaped channel that received the ribbons and compressed themtogether while forming the initial shape of the rod. Within the die, theribbons remained at a temperature of about 177° C. Upon consolidation,the resulting preform was then briefly cooled with an air ring/tunneldevice that supplied ambient air at a pressure of 1 psi. The preform wasthen passed through a nip formed between two rollers, and then to acalibration die for final shaping. Within the calibration die, thepreform remained at a temperature of about 140° C. After exiting thisdie the profile was capped with a polyether ether ketone (“PEEK”), whichhad a melting point of 350° C. The capping layer had a thickness ofabout 0.1 millimeters. The resulting part was then cooled with an airstream. The resulting rod had a diameter of about 3.5 millimeters, andcontained 45 wt. % carbon fibers, 50 wt. % PPS, and 5 wt. % cappingmaterial.

To determine the strength properties of the rod, three-point flexuraltesting was performed in accordance with ASTM D790-10, Procedure A. Thesupport and nose radius was 0.250 inch, the support span was 30millimeter, the specimen length was 2 inches, and the test speed was 2millimeters per minute. The resulting flexural modulus was about 31Gigapascals and the flexural strength was about 410 MPa. The density ofthe part was 1.48 g/cm³ and the void content was less than about 3%.Likewise, the bend radius was 3.27 centimeters.

Example 2

A rod was formed as described in Example 1, except that no cappingmaterial was employed. The rod thus contained 50 wt. % carbon fibers and50 wt. % PPS. The void content was less than about 1.5% and the bendradius was 3.86 centimeters.

Example 3

Two (2) continuous fiber ribbons were initially formed using anextrusion system as substantially described above. Carbon fiber ravings(Toray T700SC) were employed for the continuous fibers with eachindividual ribbon containing 4 rovings. The thermoplastic polymer usedto impregnate the fibers was FORTRON® PPS 205. Each ribbon contained 50wt. % carbon fibers and 50 wt. % PPS. The ribbons had a thickness ofabout 0.18 millimeters and a void fraction of less than 1.0%. Onceformed, the ribbons were then fed to a pultrusion line operating at aspeed of 20 feet per minute. Before shaping, the ribbons were heatedwithin an infrared oven (power setting of 305). The heated ribbons werethen supplied to a consolidation die having a circular-shaped channelthat received the ribbons and compressed them together while forming theinitial shape of the rod. Within the die, the ribbons remained at atemperature of about 343° C. Upon consolidation, the resulting preformwas then briefly coaled with an air ring/tunnel device that suppliedambient air at a pressure of 1 psi. The preform was then passed througha nip formed between two rollers, and then to a calibration die forfinal shaping. Within the calibration die, the preform remained at atemperature of about 140° C. After exiting this die the profile wascapped with FORTRON® PPS 320, which had a melting point of 280° C. Thecapping layer had a thickness of about 0.1 millimeters. The resultingpart was then coded with an air stream. The resulting rod had a diameterof about 3.5 millimeters, and contained 45 wt. % carbon fibers, 50 wt. %PPS, and 5 wt. % capping material.

To determine the strength properties of the rod, three-point flexuraltesting was performed in accordance with ASTM D790-10, Procedure A. Thesupport and nose radius was 0.250 inch, the support span was 30millimeter, the specimen length was 2 inches, and the test speed was 2millimeters per minute. The resulting flexural modulus was 20.3Gigapascals and the flexural strength was about 410 MPa. The density ofthe part was 1.48 g/cm³ and the void content was less than about 3%.Likewise, the bend radius was 4.37 centimeters.

Example 4

Two (2) continuous fiber ribbons were initially formed using anextrusion system as substantially described above. Glass fiber rovings(TUFRov® 4588 from PPG, which contained E-glass filaments having atensile strength of 2599 MPa and a mass per unit length of 2.2 grams permeter) were employed for the continuous fibers with each individualribbon containing 2 rovings. The thermoplastic polymer used toimpregnate the fibers was polyphenylene sulfide (“PPS”) (FORTRON® 205,available from Ticona LLC), which has a melting point of about 280° C.Each ribbon contained 56 wt % glass fibers and 44 wt. % PPS. The ribbonshad a thickness of about 0.18 millimeters and a void fraction of lessthan 1.0%. Once formed, the ribbons were then fed to a pultrusion lineoperating at a speed of 20 feet per minute. Before shaping, the ribbonswere heated within an infrared oven (power setting of 330). The heatedribbons were then supplied to a consolidation die having acircular-shaped channel that received the ribbons and compressed themtogether while forming the initial shape of the rod. Upon consolidation,the resulting preform was then briefly cooled with ambient air. Thepreform was then passed through a nip formed between two rollers, andthen to a calibration die for final shaping. Within the calibration die,the preform remained at a temperature of about 275° C. After exitingthis die, the profile was capped with FORTRON® 205. The capping layerhad a thickness of about 0.1 millimeters. The resulting part was thencooled with an air stream. The resulting rod had a diameter of about 3.5millimeters, and contained 50 wt. % glass fibers and 50 wt. % PPS.

To determine the strength properties of the rod, three-point flexuraltesting was performed in accordance with ASTM D790-10, Procedure A. Thesupport and nose radius was 0.250 inch, the support span was 30millimeter, the specimen length was 2 inches, and the test speed was 2millimeters per minute. The resulting flexural modulus was about 18Gigapascals and the flexural strength was about 590 MPa. The voidcontent was less than about 0% and the bend radius was 1.87 centimeters.

Example 5

Two (2) continuous fiber ribbons were initially formed using anextrusion system as substantially described above. Glass fiber rovings(TUFRov® 4588) were employed for the continuous fibers with eachindividual ribbon containing 2 rovings. The thermoplastic polymer usedto impregnate the fibers was Nylon 66 (PA66), which has a melting pointof about 250° C. Each ribbon contained 60 wt. % glass fibers and 40 wt.% Nylon 66. The ribbons had a thickness of about 0.18 millimeters and avoid fraction of less than 1.0%. Once formed, the ribbons were then fedto a pultrusion line operating at a speed of 10 feet per minute. Beforeshaping, the ribbons were heated within an infrared oven (power settingof 320). The heated ribbons were then supplied to a consolidation diehaving a circular-shaped channel that received the ribbons andcompressed them together while forming the initial shape of the rod.Upon consolidation, the resulting preform was then briefly cooled withambient air. The preform was then passed through a nip formed betweentwo rollers, and then to a calibration die for final shaping. Within thecalibration die, the preform remained at a temperature of about 170° C.After exiting this die, the profile was capped with Nylon 66. Thecapping layer had a thickness of about 0.1 millimeters. The resultingpart was then cooled with an air stream. The resulting rod had adiameter of about 3.5 millimeters, and contained 53 wt. % glass fibers,40 wt. % Nylon 66, and 7 wt. % capping material.

To determine the strength properties of the rod, three-point flexuraltesting was performed in accordance with ASTM D790-10, Procedure A. Thesupport and nose radius was 0.250 inch, the support span was 30millimeter, the specimen length was 2 inches, and the test speed was 2millimeters per minute. The resulting flexural modulus was about 19Gigapascals and the flexural strength was about 549 MPa. The voidcontent was less than about 0% and the bend radius was 2.34 centimeters.

Example 6

Three (3) batches of eight (8) rods were formed having different voidfraction levels. For each rod, two (2) continuous fiber ribbons wereinitially formed using an extrusion system as substantially describedabove. Carbon fiber rovings (Toray T700SC, which contained 12,000 carbonfilaments having a tensile strength of 4,900 MPa and a mass per unitlength of 0.8 grams per meter) were employed for the continuous fiberswith each individual ribbon containing 4 rovings. The thermoplasticpolymer used to impregnate the fibers was polyphenylene sulfide (“PPS”)(FORTRON® PPS 205, available from Ticona, LLC), which has a meltingpoint of about 280° C. Each ribbon contained 50 wt. % carbon fibers and50 wt. % PPS. The ribbons had a thickness of about 0.18 millimeters anda void fraction of less than 1.0%. Once formed, the ribbons were thenfed to a pultrusion line operating at a speed of 20 feet per minute.Before shaping, the ribbons were heated within an infrared oven (powersetting of 305). The heated ribbons were then supplied to aconsolidation die having a circular-shaped channel that received theribbons and compressed them together while forming the initial shape ofthe rod. Within the die, the ribbons remained at a temperature of about177° C. Upon consolidation, the resulting preform was then brieflycooled with an air ring/tunnel device that supplied ambient air at apressure of 1 psi. The preform was then passed through a nip formedbetween two rollers, and then to a calibration die for final shaping.Within the calibration die, the preform remained at a temperature ofabout 140° C. After exiting this die the profile was capped with apolyether ether ketone (“PEEK”), which had a melting point of 350° C.The capping layer had a thickness of about 0.1 millimeters. Theresulting part was then cooled with an air stream. The resulting rod hada diameter of about 3.5 millimeters, and contained 45 wt. % carbonfibers, 50 wt. % PPS, and 5 wt. % capping material.

A first batch of rods had a mean void fraction of 2.78%. A second batchof rods had a mean void fraction of 4.06%. A third batch of rods had amean void fraction of 8.74%. Void fraction measurement was performedusing CT scanning. A Metrotom 1500 (2k×2k) high resolution detector wasused to scan the rod specimens. Detection was done using an enhancedanalysis mode with a low probability threshold. Once the specimens werescanned for void fraction, Volume Graphics software was used tointerpret the data from the 3D scans, and calculate the void levels ineach specimen.

To determine the flexural fatigue life and residual flexural strength ofthe rods, three-point flexural fatigue testing was performed inaccordance with ASTM D790. The support span was 2.2 inches and thespecimen length was 3 inches. Four (4) rods from each batch were testedat a loading level of 160 Newtons (“N”) and four (4) rods from eachbatch were tested at a loading level of 180 N, respectively representingabout 50% and 55% of the pristine (static) flexural strength of therods. Each specimen was tested to one million cycles at a frequency of10 Hertz (Hz).

Before and after fatigue testing, to determine the respective pristineand residual flexural strength properties of the rods, three-pointflexural testing was performed in accordance with ASTM D790-10,Procedure A. The average pristine and residual flexural strengths ofeach batch at each loading level were recorded. The resulting pristineflexural strength for the third batch was 107 ksi, and the resultingresidual flexural strength for the third batch was 75 ksi, thusresulting in a reduction of about 29%. The resulting pristine flexuralstrength for the second batch was 108 ksi, and the resulting residualflexural strength for the second batch was 72 ksi, thus resulting in areduction of about 33%. The resulting pristine flexural strength for thefirst batch was 106 ksi, and the resulting residual flexural strengthfor the first batch was 105 ksi, thus resulting in a reduction of about1%.

These and other modifications and variations of the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention. Inaddition, it should be understood that aspects of the variousembodiments may be interchanged both in whole or in part. Furthermore,those of ordinary skill in the art will appreciate that the foregoingdescription is by way of example only, and is not intended to limit theinvention so further described in such appended claims.

What is claimed is:
 1. An umbilical for use in subsea applications, theumbilical comprising: a plurality of umbilical elements extending in alongitudinal direction; at least one reinforcing rod having a core thatcontains a plurality of thermoplastic impregnated rovings, the rovingscomprising continuous fibers oriented in the longitudinal direction anda thermoplastic matrix embedding the fibers, wherein the continuousfibers constitute from about 25 wt. % to about 80 wt. % of the core andthe thermoplastic matrix constitutes from about 20 wt. % to about 75 wt.% of the core; and an outer sheath that encloses the umbilical elementsand the reinforcing rod.
 2. The umbilical of claim 1, wherein theumbilical elements include a pipe, electrical conductor/wire, channelelement, armoring wire, or a combination thereof.
 3. The umbilical ofclaim 1, further comprising a filler that is arranged at least partlyaround and between the umbilical elements.
 4. The umbilical of claim 1,further comprising a central portion within which the reinforcing rod islocated.
 5. The umbilical of claim 1, wherein the reinforcing rod isdisposed about the periphery of the umbilical.
 6. The umbilical of claim1, wherein the umbilical contains a bundle of reinforcing rods, each ofwhich has a core that contains a plurality of thermoplastic impregnatedrovings comprising continuous fibers oriented in the longitudinaldirection and a thermoplastic matrix embedding the fibers, wherein thecontinuous fibers constitute from about 25 wt. % to about 80 wt. % ofthe core and the thermoplastic matrix constitutes from about 20 wt. % toabout 75 wt. % of the core.
 7. The umbilical of claim 1, wherein thecontinuous fibers have a ratio of ultimate tensile strength to mass perunit length of greater than about 1,000 Megapascals per gram per meter.8. The umbilical of claim 1, wherein the continuous fibers have a ratioof ultimate tensile strength to mass per unit length of from about 5,500to about 20,000 Megapascals per gram per meter.
 9. The umbilical ofclaim 1, wherein the continuous fibers are carbon fibers.
 10. Theumbilical of claim 1, wherein the thermoplastic matrix includes apolyarylene sulfide.
 11. The umbilical of claim 10, wherein thepolyarylene sulfide is polyphenylene sulfide.
 12. The umbilical of claim1, wherein the continuous fibers constitute from about 30 wt. % to about75 wt. % of the core.
 13. The umbilical of claim 1, wherein the rod hasa void faction of about 3% or less.
 14. The umbilical of claim 1,wherein the rod has a minimum flexural modulus of about 10 Gigapascals.15. The umbilical of claim 1, wherein the rod has a minimum ultimatetensile strength of about 300 Megapascals.
 16. The umbilical of claim 1,wherein the rod has a minimum tensile modulus of elasticity of about 50Gigapascals.
 17. The umbilical of claim 1, wherein the minimum bendradius of the rod is from about 1 to about 30 times the outer diameterof the rod, determined at a temperature of about 25° C.
 18. Theumbilical of claim 1, wherein the minimum bend radius of the rod is fromabout 0.5 to about 10 centimeters, determined a temperature of about 25°C.
 19. The umbilical of claim 1, wherein the core contains from 4 to 20rovings.
 20. The umbilical of claim 1, wherein the rovings aredistributed generally symmetrically about a longitudinal center of thecore.
 21. The umbilical of claim 1, wherein each roving contains fromabout 1,000 to about 50,000 individual continuous fibers.
 22. Theumbilical of claim 1, wherein the rod has a diameter of from about 0.1to about 50 millimeters.
 23. The umbilical of claim 1, furthercomprising a capping layer that surrounds the core.
 24. The umbilical ofclaim 1, wherein the rod has a substantially circular cross-sectionalshape.
 25. An umbilical for use in subsea applications, the umbilicalcomprising: a plurality of umbilical elements extending in alongitudinal direction, wherein the umbilical elements include a pipe,electrical conductor/wire, channel element, armoring wire, or acombination thereof; a filler that is arranged at least partly aroundand between the umbilical elements; at least one reinforcing rod havinga core that contains a plurality of thermoplastic impregnated rovings,the rovings comprising continuous carbon fibers oriented in thelongitudinal direction and a thermoplastic matrix embedding the fibers,wherein the continuous carbon fibers constitute from about 30 wt. % toabout 75 wt. % of the core and the polyphenylene sulfide matrixconstitutes from about 25 wt. % to about 70 wt. % of the core; and anouter sheath that encloses the umbilical elements, the filler, thereinforcing rod.